Viruses in marine brown algae

Virus-like particles have been repeatedly reported from multicellular marine red and brown algae, and the release of viruses from infected algal hosts into the surrounding sea water also contributes to the number of virus-like particles in coastal waters. It has become apparent that they are intimately and unseparably connected with the biology of their host organisms. This chapter reviews investigations on this newly discovered group of brown algal viruses. Axenic algal clones with desired growth properties are selected and grown in large quantities in laboratories for anlaysis. In experiments, glass beads are used in a Braun homogenizer to disrupt fresh diseased plant material. After removal of cellular debris by low-speed centrifugation, viral material was precipitated in polyethylene glycol and further purified by equilibrium centrifugation in cesium chloride gradients. The virus particles in these preparations were morphologically less complex than those seen in thin sections through infected cells. Pulsed-field agarose gel electrophoresis (PFGE) is used to determine the size of the viral genome. Pulsed-field gel electrophoresis demonstrated that in addition to EsV, other brown algal viruses also possess large double-stranded DNA as genomes, although their sizes differ significantly among species. On the basis of observations, the interesting possibility remains that brown algal viruses can serve in some cases as carriers for the transmission of foreign genetic information. © 1998 Academic Press Inc.